WO2014040155A1 - Metal member of a moving system of an internal combustion engine and method for manufacturing the metal member - Google Patents

Description

 Report of the Invention Patent for "METAL MEMBER OF A MOBILE MOTOR SYSTEM FOR INTERNAL COMBUSTION AND MANUFACTURING PROCESS OF THIS METAL MEMBER".

 The present invention relates to a method of manufacturing a metal member of a movable combustion engine system (above all a piston ring) and a metal member undergoing such a manufacturing process.

 Such a manufacturing process is configured to alter the physicochemical properties of the material that constitutes this metal member, providing a component with greater efficiency in terms of operation and longer life in terms of use.

Description of the prior art

 In an internal combustion engine (be it Diesel cycle, Otto cycle, two or four stroke) the piston ring is the part that fulfills the function of sealing the space between the sleeve and the piston piston, isolating the chamber. other internal engine components.

 The piston ring is arranged radially at the base of the cylinder, preventing combustion gases from escaping out of the combustion chamber toward the crankcase and preventing engine oil from penetrating the combustion chamber in a reverse path. There may be more than one piston ring surrounding a single piston, and it is quite common to use two or three rings arranged parallel to the piston base.

 To fulfill this role efficiently, the piston ring must have a finely smooth outer finish and should be made of a material of relatively high hardness. This is because, according to experimental evidence, the harder the outer surface of the ring - especially the surface that comes into contact with the inner face of the sleeve - the greater its sealing efficiency.

In order to keep the outer ring finish smooth and to give it greater hardness, piston rings (usually made of carbon steel) undergo one or more surface treatments such as: PVD - Physical Vapor Deposition;

 CVD - Chemical Vapor Deposition;

 Nitriding;

 (Among others)

 Generally, these treatments promote a higher degree of hardness on a given metal surface by inserting external elements into the metal crest structure. These external elements may be, for example, the nitrogen or carbon atom.

 It is noted that such finishing processes do not interfere with the internal hardness of the metal, that is, the hardness in the innermost layers of a metal part. These surface treatments are capable of modifying only the outermost layer of a part, forming a supersaturated micrometer thickness film of external elements amidst the original crystallographic structure of the metal (hereinafter, coating film).

 However, while increasing the hardness of a given metal surface, these surface treatments, per se, are not capable of promoting the creation of a highly efficient and durable piston ring. This is because, after these treatments are performed, the rings become quite fragile, especially at the points of intersection between the outer shell (ie the coating film) and the core of the metal part.

 This fragility is mainly due to the heterogeneity established between these two layers of material. As these two layers have different materials (one has a higher concentration of external elements than the other) they also reveal different physical properties, such as: coefficient of expansion, strength, compression ratio, etc.

This is where a major problem with state of the art piston rings lies. The line dividing the two layers, defined by the contrast between the outermost layer and the innermost layer of metal, can easily give rise to a crack. This crack can propagate through the workpiece, resulting in the peeling / peeling of the metal and, consequently, the total loss of the piston ring outer layer. By losing its outermost layer, the piston ring abruptly decreases its longevity and efficiency, allowing undesirable fluid exchange between the combustion chamber and the innermost region of the engine block and increasing the susceptibility to wear of the outer face of the ring. . Therefore, a solution to this problem is needed. A solution designed to increase the longevity and efficiency of a piston ring by physically or chemically treating the crystallographic structure of an already hardened piston ring.

Objectives of the Invention

 The present invention is directed to the design of a durable and sealing efficient piston ring.

 The present invention also has as its object the creation of a durable and sealing efficient piston ring manufacturing process.

 The present invention also aims to create a metal member of a mobile system of an internal combustion engine, which reveals efficiency and durability in terms of use.

 Finally, the present invention is also directed to the design of a method of manufacturing a metal member of a mobile combustion engine system as disclosed above.

Brief Description of the Invention

 The objects of the present invention are achieved by a metal member of a movable system of an internal combustion engine that has undergone surface infiltration hardening treatment of an external element amid the crystallographic structure of the metal by the laser process by least a portion of its outer surface.

The objectives of the present invention are also achieved by a method of manufacturing a metal member of a mobile system of an internal combustion engine consisting of a single step comprising two simultaneous occurring operations, namely: a surface treatment of hardening by infiltration of an external element into the crystallographic structure of the metal; and the formation of a diffusion zone between the original metal substrate and its saturated zone by applying a laser on its outer surface.

Brief Description of the Drawings

 The present invention will hereinafter be described in more detail based on an exemplary embodiment shown in the drawings. The figures show:

 Figure 1 is a cross-sectional view of a first sample of a piston ring that has been subjected to the treatment process of the present invention.

 Figure 2 is a cross-sectional view of a second sample of a piston ring that has been subjected to the treatment process of the present invention.

 Figure 3 is a graph showing the shear strength index of the material of a piston ring of the present invention as compared to a prior art piston ring.

 Figure 4 - is a graph showing the hardness variation of the material that makes up the piston ring, as analyzed from its outermost layer towards its core.

Detailed Description of the Figures

 The basic principle of the piston ring manufacturing process 1 of the present invention is the application of a high intensity laser on the outer radial face of the piston ring 1.

 When applied under rigid conditions, the laser causes the outer element that is saturated in the outer radial layer of the ring to be diffused into the inner layers of this material, thereby creating a gradient of outer element concentration over successive layers of material. that constitute this ring.

 Figures 1 and 2 of this report show micrographs of two piston ring samples that have undergone the laser treatment of the present invention.

Through these two photographs you can see: an outer band, which corresponds to the cross section of a sheet of paper aluminum 3 (used only to allow differentiation of bakelite - black upper region - from the beginning of the coating); a "saturated zone 4" or coating film; a "substrate 2" corresponding to the constituent metal of piston ring 1 in its original form (generally carbon steel); and a "diffusion zone 5" which corresponds to a hybrid material between substrate 2 and saturated zone 4.

 This diffusion zone 5 may be defined as an intermediate layer between saturated zone 4 and substrate 2, which is formed after the laser application process under the outer radial face of the piston ring 1.

 It is noted that by promoting cladding / alloying between substrate 2 and coating film materials, the laser undoes the cracks and tears susceptible points originally existing between the coating film and the ring core piston

 The diffusion zone 5 creates a gradual transition between the physical properties of the coating film and the substrate 2 (or core) of the material. This is where the main quality attributed by applying the laser to the piston ring 1 lies.

 An experiment performed with a sample of a piston ring 1 revealed that starting from the outer radial surface of the ring to a depth of 100 microns (penetrating toward the radial center of this ring) the hardness of its material is gradually decreased as shown in graph of figure 4 of this report.

 A secondary feature resulting from the application of the laser on the piston ring 1, in addition to the creation of a diffusion zone 5, is the refining of the grains of its metal structure on its outer radial surface.

On the outer radial face of the piston ring, the face most affected by laser application, a temporary fusion of the metal occurs. This fusion, occurring only within a micrometer thickness range of the outer face of the ring, is rapidly cooled by the remainder of piston ring 1 (which is at room temperature). This heating followed by rapid cooling is what causes the grain of the metal structure to shrink, a phenomenon known as grain refinement. By decreasing the grain size of the metal frame, the laser increases the fracture resistance of the ring even further. This is due to the fact that any metal structure that has its reduced grain size expands its elastic deformation limit thus avoiding unwanted occurrences such as peeling / peeling of the material surface.

 At the end of the laser application process, piston ring samples often show a much higher scuffing index than that of conventional prior art rings, as shown in the graph in Figure 3 of this report. .

 The laser should be applied at such a speed and intensity as to allow the outer layer of the ring to fuse, but not to evaporate this element. It should be noted that the slower the laser application rate, the greater the degree of diffusion of the outer element and consequently the more diluted, i.e. the less saturated the coating film material will be. Preferably, the speed and intensity of laser application should be sufficient to form a diffusion zone 5 of approximately 80 m (any value between 30 and 150 microns being considered a reasonable value).

 However, the intensity of the laser and its speed of application are not the only factors that affect the result of its application on the outer face of the ring. Besides the speed and intensity of the laser, other factors that affect the efficiency of this treatment are: the laser angle of incidence; the gaseous environment of the laser operating room; and the thickness of the coating film.

Preferably, the most suitable parameters for the application of this laser are shown in the following table: Preferred application parameters:

 incidence angle of between 45 ° and 90 °

 laser:

 application speed between 2 and 20 mm / s

 Laser

 laser power: between 2 and 8 KW

 blur: between 8 and 300 mm

 e-C02 or Nd appliance model: YAG or laser dimmer: from HDPL or fiber

Aimed at the initial surface treatment process to which piston ring 1 is subjected, it is known that this laser treatment process is capable of promoting good results to metal rings whose coating film is saturated with cobalt, nickel, chromium, boron. , nitrogen, carbon or a combination thereof. These elements can be obtained from carbides, sulphides or nitrides, just to name a few forms of applicable industrial inputs.

 In any case, it should be noted that the laser application process of the present invention is not restricted to the rings hardened by the infiltration of these external elements, but other forms of application are possible provided that they include the concept of diffusion defined in this report. .

 As for the materials which preferably (not necessarily) should be the substrate 2 of piston ring 1, are metals, or alloys, mostly made of iron or aluminum.

In its preferred embodiment, the process of hardening the outer layer of piston ring 1 and applying the laser constitute a single step. In other words, the insertion of the outer element into the crystallographic structure of the metal occurs simultaneously with the application of the laser which two following phenomena occur simultaneously: the hardening of the outer face of the ring and the creation of a gradient (ie a zone of diffusion 5). Such an operation can be performed, for example, by spraying a particulate containing the outer element onto the heated incandescent metal during laser application.

 It is noted that, by the processes and manufacturing methods disclosed above, the present invention can solve all the problems it is intended to solve, namely: the problems related to the low sealing efficiency and the low longevity of the piston ring 1 of the state of the art.

 The present invention further discloses a secondary advantage due to the ecological benefit it brings in one of its possible embodiments. This is because, in the process of inserting the carbon element into the metal crest structure, it is possible to use a material called carbon black.

 Carbon black is a byproduct of pyrolysis (controlled burning) of automotive tires. Its use in an industrial process such as this one of the present invention is quite beneficial for the environment, as by "trapping" carbon atoms in the crest structure of a metal, the present invention prevents these atoms from eventually being decomposed into dioxide or monoxide. which are very environmentally harmful air pollutants.

 Finally, it is worth noting that while this report to this point refers only to the piston ring, it is evident that the manufacturing method described in these sheets can also be applied to any other component of an internal combustion engine.

 Other possible components that may make use of this manufacturing process include, for example, the piston sleeve, the intake and exhaust valves, the piston pin and its housing cavity, the connecting rod, the various crankshaft parts, and so on. other parts. Note that any part that moves or is in contact with a part that moves internally to a combustion engine may receive the treatment described in this report.

In this way a piston jacket can be treated with surface (the face that will contact piston ring 1 during engine operation) and be subjected to a laser application in order to have the same effects already described in this report, namely the creation of a diffusion zone 5 between the coating film and the core of the material and the grain refinement in proximity to this coating film.

 Thus, it should be noted that the present invention generally protects metal members of a movable system of an internal combustion engine as well as the methods of manufacturing such metal members. Among these metal members of a mobile system, once again, it is worth mentioning, for example, the piston sleeve and piston ring 1, as well as other components of a combustion engine that could benefit from the manufacturing process proposed in this report. .

 Having described a preferred embodiment example, it should be understood that the scope of protection of the present invention encompasses other possible variations and is limited only by the content of the appended claims, including the possible equivalents thereof.

Claims

 1. Metal member of a movable system of an internal combustion engine, characterized in that this metal member is subjected to surface hardening treatment by infiltration of an external element into the crystal structure of the metal by the laser process, at least least a portion of its outer surface.  Metal member according to Claim 1, characterized in that it consists of a piston ring (1).  Metal member according to claim 1, characterized in that it consists of a piston sleeve.  Metal member according to Claim 1, characterized in that it consists of iron, aluminum or a metal alloy composed predominantly of one of these elements.  Metal member according to claim 1, characterized in that the external element is cobalt, nickel, chromium, nitrogen, boron carbon or a combination thereof.  Metal member according to Claim 1, characterized in that the raw material used to obtain the external element is a carbide, a sulfide, a nitride or carbon black.  Metal member according to Claim 1, characterized in that it comprises a diffusion zone (5) disposed between the coating film and the core of this part, said diffusion zone (5) having a thickness of between 30 and 150 microns.  8. Method of manufacturing a metal member of a mobile system of an internal combustion engine, characterized in that it consists of a single step comprising two simultaneous occurring operations, namely:  performing a surface hardening treatment by infiltration of an external element into the crystallographic structure of the metal; and - the formation of a diffusion zone (5) between the substrate (2) metal and its saturated zone (4) by applying a laser to its outer surface.  Method of fabricating a metal member of a movable system of an internal combustion engine according to Claim 8, characterized in that the laser applied to the outer surface of the metal member focuses on its surface at an angle between 45 ° and 90 °; at an application speed of between 2 and 20 mm / s; at a power of between 2 and 8 kW; and at a blur of between 8 and 300 mm.